Method of an apparatus for filling a fuel injection pump

ABSTRACT

Method of and apparatus for filling a piston fuel injection pump of internal combustion engines with fuel. The fuel is fed through a side filling channel into a space over the piston which is under negative gauge pressure during the movement of said piston to its lower dead center, as well as during its movement toward its upper dead center until the filling channel is covered by the edge of the piston at the moment when there is still negative gauge pressure in the area above the piston. During the subsequent displacement of the piston to the upper dead center, the negative pressure in said space disappears and the fuel starts being discharged into the delivery conduit. The volume of fuel flowing through the filling channel is adjustable by varying the entering pressure of the fuel.

O United States Patent 1 1 [1 11 3,834,838

Indra Sept. 10, 1974 [54] METHOD OF AN APPARATUS FDR 2,888,876 6/1959Nichols 417/490 FILLING A FUEL INJECTION PUMP FOREIGN PATENTS ORAPPLICATIONS 1 lnvemorl Jammir Brno, 1,357,519 2/1964 France 417/490Czechoslovakia [73] Assignee: Vysoke uceni technicke v Brne, PrimaryExaminerWilliam L. Freeh Brno, Czechoslovakia Assistant Examiner-RichardE. Gluck [22] Filed: Mar. 22, 1972 21 Appl. No.: 237,141 [57] ABSIRA CTMethod of and apparatus for filling a piston fuel injection pump ofinternal combustion engines with fuel. [30] Forelgn Apphcauon Pm mtyData The fuel is fed through a side filling channel into a Mar. 24,Czechoslovakia pace over the piston is under negative gauge pressureduring the movement of said piston to its U-S. lower dead center as weas during its movement to- [51] Int. Cl. F04b 7/04, F04b 39/10 ward itsupper dead center until the fining channel is [58] F leld of Search417/490, 501, 53, 494, covered by the edge f the piston at the momentwhen 417/499 252; 123/139 AA, 139 there is still negative gauge pressurein the area above 139 AB, 139 139 R the piston. During the subsequentdisplacement of the piston to the upper dead center, the negativepressure [56] References C'ted in said space disappears and the fuelstarts being dis- UNITED STATES PATENTS charged into the deliveryconduit. The volume of fuel 2,522,390 9/1950 Peterson 417/252 x flowingthrough t filling Channel is adjustable y 2,642,804 0/1953 Bowers417/252 varying the entermg pressure of the fuel. 2,727,493 12/1955Reiners 123/32 R 10/1957 Aldinger 123/139 R 2 Claims, 2 Drawmg Flgul'es1 l M Q METHOD OF AN APPARATUS FOR FILLING FUEL INJECTION PUMP Thepresent invention relates to a method of filling a piston fuel injectionpump for internal combustion engines, and to an injection pump forperforming such method.

The volume of injected fuel charges of known piston injection pumpdelivered by one piston stroke is changed by means of turning thepiston, which is made as a sleeve valve in its upper part, and isprovided with a helical change regulating edge. The pump cylinder isprovided with at least one radial filling channel. As the pump pistonmoves from its lower dead center, the fuel which has been sucked intothe cylinder through the said filling channel is bypassed back to thefuel source until the upper edge of the piston covers that channel.Subsequently, an effective discharge of the pump into the deliveryconduit and to the delivery nozzle begins; the discharge lasts until theregulating edge of the piston has uncovered the said filling channelagain. From this moment on, until the upper dead center of the piston isreached, the fuel from the cylinder is again by passed to the fuelsource, i.e., filling chamber through the filling channel.

The main feature of this system consists in that a part of thedischarged fuel is bypassed before, and a part of the fuel is bypassedafter the effective discharge. The bypassing of fuel, especially afterthe effective discharge has been terminated, is performed at highspeeds, particularly in the case of large pumps; this is the case ofcavitation erosion on the sealing surface of the piston above theregulating edge. The damage to the sealing surface of the piston due tothis type of erosion is so severe that the piston must periodically beexchanged.

Another feature of such system is the fact that only a small sealingsurface of the piston is available opposite the filling channel when thepiston is adjusted for small injection charges. Particularly in the caseof large diameter pistons, the tightness of individual pistons in thisarea appears to be very irregular, thus causing serious trouble whenpumps for multi-cylinder engines must be adjusted.

It is, therefore, an object of the present invention to create a pumpwithout any bypassing of fuel from the cylinder before or after theeffective discharge of fuel, thus preventing the above-discussedcavitation erosion from taking place, while insuring excellent pistontightness both for large and for small charges of injected fuel.

In the method according to the present invention the fuel is fed to thenegative gauge pressure area above the piston through the side fillingchannel during the displacement of the piston to the lower dead centerand also during movement of the piston toward its upper dead center,until the filling channel is covered by the edge of the piston, whilethere is still negative gauge pressure, that is, sub-atmosphericpressure, in the area above the piston. Thereupon, during the subsequentdisplacement of the piston to the upper dead center, the negative gaugepressure in the pump cylinder disappears, and the fuel starts beingdischarged into the delivery conduit; the volume of fuel flowing throughthe filling channel is adjustable, so as to vary the volume of the fuelcharges.

It is further advantageous when the discharge of fuel into the deliveryconduit begins {after the piston has covered the filling channel), whenthe piston has travelled a distance equalling from one half to one fullstroke of the piston during the active fuel delivery.

An object of the apparatus for performing the method according to thepresent invention consists in that the body is provided with a fillingchannel preceded by a throttling nozzle or orifice providing means, saidchannel being connected with the filling chamber.

The foregoing and other features of the invention set out in theappended claims are incorporated in the specifica embodiment hereinafterparticularly described with reference to the accompanying drawings inwhich:

FIG. 1 diagrammatically shows the axial section of the whole injectionpump, and

FIG. 2 is a view in section on an enlarged scale of a part of the pumparound the filling channel.

A smooth piston lapped into the pump body 2 is pushed to displacement bythe cam 3 through the action of the lifting element 4 with a roller, thepiston being returned directly by a coil compression spring 5. A reliefdelivery valve 6 of known construction, represented as a ball valve inorder to simplify the drawing, is accommodated in the body 2 above thepiston 1. At the side a lateral filling channel 7 debouches into thearea above the piston, said filling channel being drilled in the body 2,preceded by a throttle nozzle or orifice providing insert 8. Means isprovidedto deliver fuel at a controlled constant pressure to a fillingchamber 9 in the body 2 in advance of the throttling nozzle8. As anon-limiting example of such means there is shown in FIG. 1 aconventional constant pressure outlet valve 15 interposed in the conduit14 which supplies fuel to filling chamber 9. As indicated, valve 15delivers fuel under constant pressure, such constant pressure beingadjustable by adjustment of valve 15.

The fuel discharge by piston 1 through the delivery valve 6 is deliveredthrough the channel 10 and the adjacent discharge piping 12 to aninjection nozzle (not shown).

As the piston 1 moves from its upper dead center downwards under theaction of spring 5,, the delivery valve 6 closes and vacuum is createdabove the piston the area is now filled with vapors of fuel left overthe piston. From the moment when the upper edge of piston 1 startsopening the lateral filling channel 7, the fuel from the filling chamber9 begins streaming through the throttle valve 8 into the evacuated spaceabove the piston. The fuel is brought to the filling chamber 9 under anoverpressure which is adjustable as required. The filling of the spaceabove the piston l continues until piston I has passed through its lowerdead center (see position I of piston l as represented in FIG. 2), anduntil its upper edge 11 has again fully covered the lateral fillingchannel 7.

The value of the pressure of the fuel fed to the filling chamber 9 iscontrolled so as always to prevent the evacuated space above the piston1 from being filled with liquid fuel during the filling period when.theengine. is running. For that reason the piston 1 must perform, inaddition, a certain stroke a (FIG. 2) during its movement upwards, inorder that the fuel vapors above the piston 1 may disappear and thewhole space above the piston 1 shall become filled with liquid fuelonly.

See position ll of piston l, as shown in FIG. 2. From this moment on,the effective displacement of fuel takes place, as marked by the strokefrom the space above piston 1 over the delivery valve 6 to the upperdead center of the piston 1. See position Ill in FIG. 2. As the piston 1moves from the upper dead center downwards, the whole described processis repeated.

Under conditions of rated fuel delivery, the stroke a =O.5 to l ofstroke b, in order to insure sufficient tightness of piston 1, whilepreventing pressure shocks from being transmitted from the space abovethe piston l to the filling chamber 9.

Provided the injection pump is to deliver smaller injection charges offuel than the rated charge, fuel is brought to the filling chamber 9under decreased over pressure. During the filling period, then, asmaller volume of fuel streams to the low pressure space above thepiston l and, consequently, the fuel vapors during the subsequentpulling stroke of the piston 1 disappear later, thus leaving only asmaller stroke of piston l for effective fuel displacement. If the fueldelivery into the filling chamber 9 is cut, the delivery of fuel to theinjection pump is stopped. For the starting speed of the engine, suchfilling of the space above the piston l with liquid fuel can be obtainedby adjusting the pressure in the filling chamber 9 so that effectivefuel displacement begins immediately after the channel 7 has beencovered by the upper edge 11 of the piston 1. Thus an increase of thestarting charge delivery as compared to the rated charge delivery isreached, which contributes to the facilitating of cold engine starts.

Moreover, besides the above-mentioned advantages of better pistontightness and of eliminating the sources of cavitation erosion at thepiston, among further advantages of the injection pump of the inventionthere should be mentioned a simpler design of the piston l, and itslonger service life. There is further attained a considerablesimplification of the whole injection pump based on the fact that therelatively complicated mechanism for turning the piston l, exacting fromthe viewpoint of production technology and indispensable for the currentinjection pumps, can be altogether eliminated.

Although the invention is illustrated and described with reference toone preferred embodiment thereof. it is to be expressly understood thatit is in no way limited to the disclosure of such a preferredembodiment, but is capable of numerous modifications within the scope ofthe appended claims.

What is claimed is:

l. A reciprocating piston fuel injection pump for in ternal combustionengines said pump comprising a pump cylinder, a piston reciprocable inthe cylinder between its upper dead center and its lower dead center,means for reciprocating the piston, a side filling channel in thecylinder intermediate the upper and lower dead centers of reciprocationof the piston therein, the cylinder and the fluid displacing end to thepiston presenting a space therebetween, the fluid displacing end of thepiston having an edge which covers and seals the filling channel duringmovement of the piston toward its upper dead center, a fuel fillingchamber external of the cylinder, a fuel conducting conduit meansbetween the filling chamber and the end of the filling channel removedfrom the space in the cylinder, a throttling orifice means interposed insaid conduit means, and means to subject the fuel in the filling chamberto positive pressure, the parts being so constructed and arranged thatnegative gauge pressure exists in the space in the cylinder when thefilling channel is completely covered by said edge of the piston duringthe upward movement of the piston, and negative gauge pressure iseliminated from said space by further upward movement of the piston.

2. A fuel injection pump according to claim 1, comprising means to varythe pressure to which the fuel is subjected in the filling chamber.

1. A reciprocating piston fuel injection pump for internal combustionengines said pump comprising a pump cylinder, a piston reciprocable inthe cylinder between its upper dead center and its lower dead center,means for reciprocating the piston, a side filling channel in thecylinder intermediate the upper and lower dead centers of reciprocationof the piston therein, the cylinder and the fluid displacing end to thepiston presenting a space therebetween, the fluid displacing end of thepiston having an edge which covers and seals the filling channel duringmovement of the piston toward its upper dead center, a fuel fillingchamber external of the cylinder, a fuel conducting conduit meansbetween the filling chamber and the end of the filling channel removedfrom the space in the cylinder, a throttling orifice means interposed insaid conduit means, and means to subject the fuel in the filling chamberto positive pressure, the parts being so constructed and arranged thatnegative gauge pressure exists in the space in the cylinder when thefilling channel is completely covered by said edge of the piston duringthe upward movement of the piston, and negative gauge pressure iseliminated from said space by further upward movement of the piston. 2.A fuel injecTion pump according to claim 1, comprising means to vary thepressure to which the fuel is subjected in the filling chamber.